CIRCADIAN CONTROL OF VISUAL INFORMATION-PROCESSING IN THE OPTIC LOBE OF THE GIANT COCKROACH BLABERUS-GIGANTEUS

Extracellular spike activity from three different types of visual inte rneurons found in the optic lobe of the giant cockroach Blaberus gigan teus was recorded. The spike rate of all three types of neurons fluctu ated in a circadian manner in constant darkness (DD). Two types, so-ca lled ''on'' neurons (ON1 and ON2), responded exclusively to stationary light stimuli. A static light pulse elicited a sustained component in ON1, whereas in ON2 only a brief transient response was observed. In ON1 neurons, responsiveness was high during the subjective night and l ow during the subjective day. The responsiveness of ON2 neurons had a peak during a few hours around subjective dusk and a smaller peak in t he later subjective night. The third neuron type recorded consisted of a directionally selective motion-detecting (DSMD) neuron. The pure in tensity response and the motion response of the DSMD neuron were high during the subjective day and low during the subjective night. The res ults show that visual interneurons in the optic lobes are influenced d ifferently by the circadian oscillator system. It is suggested that th e mode of circadian control depends on the role a neuron plays in the process of visual information processing.